Sputum Biomarkers in Wood and Tobacco Smoke Etiotypes of Chronic Obstructive Pulmonary Disease

Figures & data

Table 1 Demographic and Clinical Characteristics of the Women Participating in the Study

Characteristic	WS-COPD (N = 31)	TS-COPD (N = 29)	Control (N = 28)	P-value (WS vs TS)
Age, years	76 ± 8	68 ± 8	61 ± 13	<0.001^a
Height, cm	149 ± 7	153 ± 7	151 ± 7	0.02^a
BMI, kg/m^2	29.2 ± 4.8	27.7 ± 6.1	30 ± 4.4	0.29^a
Pack/year Index	-	30 [43]	-
Wood smoke exposure, years	20 [20]	-	-
FEV1 post β2 (% predicted)	74% ± 19	67% ± 22	115% ± 19	0.19^a
FEV1/FVC post β2	0.59 ± 0.08	0.52 ± 0.13	0.80 ± 0.05	0.02^a
Treatment
Inhaled corticosteroids	21 (67%)	19 (65%)	-	0.99 ^b
Inhaled anticholinergics	26 (84%)	22 (76%)	-	0.65 ^b
Inhaled LABA	23 (74%)	15 (52%)	-	0.12 ^b
Long-term oxygen therapy^d	9 (29%)	11 (41%)	-	0.65 ^b
Classification of COPD by GOLD^e
I	13 (41%)	9 (31%)	-	0.54 ^b
II	14 (45%)	11 (37%)	-	0.76 ^b
III	4 (12%)	8 (27%)	-	0.27 ^b
IV	0	1 (3%)	-	0.99 ^b

Notes: Demographic, clinical, and functional variables are expressed as mean ± standard deviation; Pack/year Index and wood smoke exposure are expressed as median [interquartile range]; treatment and classification by GOLD are expressed as number and proportions: n (%). ^aP value from Student’s t-test (two-tailed). ^bP value from Fisher Exact-test (two-tailed). FEV₁ less than 30% of the predicted. ^dOxygen utilization during more than 15 hours per day; ^eGOLD Classification for COPD: I mild: FEV₁ ≥ 80% of predicted; II moderate: FEV₁ ≥50% – <80% of the predicted; III severe: FEV₁ ≥30% – <50% of the predicted.

Abbreviations: WS-COPD, COPD due to wood smoke exposure; TS-COPD, COPD due to tobacco smoke exposure; BMI, Body mass index. Pack/year Index, number of cigarettes smoked per day multiplied by the number of years smoking and divided by 20; FEV₁, Forced expiratory volume in the first second; FVC, Forced vital capacity; β₂, Beta-2-agonist bronchodilator; LABA, long-acting β₂-agonist; GOLD, Global Initiative For Chronic Obstructive Lung Disease. IV, very severe.

Table 2 Concentration of Biomarkers in Women with COPD from Wood Smoke (WS), Tobacco Smoke (TS) and Healthy Controls

Biomarker	WS-COPD (N=31)	TS-COPD (N=29)	Control (N=28)	P-value^a	P-value^b
MMP- 9 (ng/mL)	1089 (4600)	1843 (6419)	364 (1931)	0.013	0.29
CCL5 (pg/mL)	1.50 (0.79)	1.97 (2.0)	1.10 (0.58)	0.003	0.03 ^c
IL-8 (pg/mL)	0.28 (0.2)	0.25 (0.08)	0.21 (0.02)	< 0.001	0.11
VEGF-1 (pg/mL)	0.055 (0.01)	0.056 (0.01)	0.050 (0.01)	0.22	0.87
CCL16/HCC-4 (pg/mL)	0.002 (0.0001)	0.002 (0.0001)	0.002 (0.0001)	0.27	0.99

Notes: All variables are expressed as median (IQR: Interquartile range [75 percentile-25th percentile]). ^aP value from Kruskal–Wallis non-parametric test (two-tailed) comparing WS-COPD, TS-COPD, and controls; ^bP value from Robust Regression (two-tailed) comparing WS-COPD and TS-COPD and adjusting for potential confounders, that is variables associated with the exposure (WS-COPD/TS-COPD) and the outcome (biomarker): MMP-9 adjusted by FEV₁ (forced expiratory volume in one second) post-bronchodilator percent predicted, ICs (inhaled corticosteroids), LABA (long-acting beta-agonist), statins, height, CCL5 adjusted by FEV₁ post-bronchodilator percent predicted, ICs, LABA, statins, IL-8 adjusted by FEV₁/FVC (forced vital capacity) post-bronchodilator, LABA, statins, VEGF-1 adjusted by FEV₁ post-bronchodilator percent predicted, ICs, LABA, statins, CCL16 adjusted by FEV₁ post-bronchodilator percent predicted, ICs, LABA, statins, age. ^cApplying the Bonferroni correction (significance level of 0.025), this P value approaches the threshold of statistical significance.

Abbreviations: WS-COPD, COPD from exposure to wood smoke; TS-COPD, COPD from exposure to tobacco smoke; MMP-9, Matrix metalloproteinase 9; CCL5, chemokine ligand 5; CCL16/HCC-4, chemokine ligand 16/hemofiltrate CC chemokine 4; IL-8, Interleukin 8, VEGF-1, vascular endothelium-derived growth factor. Concentrations; pg/mL, picograms /millilitre; ng/mL, nanogram/millilitre.

Figure 1 Cytokine levels by Group. (A) CCL5; (B) IL-8; (C) MMP-9; (D) VEGF-1.

Notes: P values using two-tailed Mann–Whitney U-Test, exact method. For comparison of WS-COPD and TS-COPD, we used de Bonferroni correction.

Abbreviations: TS-COPD, COPD from exposure to tobacco smoke; WS-COPD, COPD from exposure to wood smoke; MMP-9, matrix metalloproteinase 9; CCL5, chemokine ligand 5; IL-8, Interleukin 8, VEGF-1, vascular endothelium-derived growth factor-1; pg/mL, picograms/millilitre, ng/mL: nanogram/millilitre.

Table 3 Correlation Between the Levels of Biomarkers and the Degree of Airflow Obstruction

Biomarker	Spearman Correlation Coefficient (Rho)	95% CI (Rho)	P-value^a
MMP-9 vs FEV1 post β2 (% pred)	−0.26	−0.46 to −0.04	0.016
CCL5 vs FEV1 post β2 (% pred)	−0.37	−0.56 to −0.15	0.001
IL-8 vs FEV1 post β2 (% pred)	−0.42	−0.61 to −0.21	<0.001
CCL16/HCC-4 vs FEV1 post β2 (% pred)	−0.12	−0.32 to 0.13	0.29
VEGF-1 vs FEV1 post β2 (% pred)	−0.22	−0.43 to −0.001	0.04

Abbreviations: (Rho) Spearman correlation coefficient with 95% Bootstrap Confidence Intervals. ^a P value (two-tailed) is considered significant at P < 0.05.

Abbreviations: 95% CI, 95% confidence interval of the Spearman correlation coefficient; MMP9, matrix metalloproteinase 9; CCL5, chemokine ligand 5; CCL16/HCC-4, chemokine ligand 16/hemofiltrate CC chemokine 4; Il-8, Interleukin 8; FEV₁, Forced expiratory volume in the first second; β₂, beta-2-agonist bronchodilator; % pred, percentage of the predicted value.